For years, Twitter has offered both a website and mobile apps for iPhones and Android. But in 2017, it decided to marry the two approaches. The result is one of the highest-profile examples of what's called a progressive web app, a technology that could rejuvenate the web and challenge the power of app stores.
The web got its start as a place for static documents studded with hypertext links to other websites. But over the last two decades, it's become steadily more interactive. For many of us, a web browser is mostly all we need on our laptops. But on mobile devices, apps that use interfaces built natively into Apple's iOS and Google's Android rule the roost.
Twitter's choice to offer a progressive web app, or PWA, shows what's possible on the web now. The company likes its native apps, but says its PWA is good for quickly bringing new people to Twitter.
"The web works everywhere," said Charlie Croom, a Twitter software engineer who helped build the company's web app. "It's the lowest barrier to entry and most of our users' first experience."
PWAs employ new web programming abilities championed by Google and allies like Microsoft that make interactive websites behave more like regular phone apps. PWA abilities include things like working even when you don't have a network connection, launching with a tap on a home-screen icon, sending you alerts with push notifications and synchronizing data in the background for snappy startup.
Those abilities are at the heart of tension between Google and Apple over the future of the web. Google wants a powerful, interactive web, and is building abilities into its . But Apple, which holds a lock on web technology used on iPhones and iPads, is moving more slowly and cautiously. At stake is whether the web will become a thriving, central part of our mobile lives or be relegated to a useful but secondary role.
Web app fans
There are plenty of web app fans besides Twitter, including Uber, travel site Trivago and Indian e-commerce site Flipkart. Starbucks saw its website usage double after it rolled out a PWA, and eBay is finding the technology useful even though it hasn't gone whole hog for the idea. One of Google's biggest PWA allies is Microsoft, which offers PWAs of its own and sees the design as a good way to run software on Windows. "We're quite bullish about making web applications feel more native," said Microsoft Edge leader Chuck Friedman.
Web apps hold a starring role in Google's Project Fugu, an effort to dramatically increase browser abilities. In order to fulfill its potential, though, Fugu partners such as Microsoft and Intel have to convince Apple to embrace features like push notifications, file system access and app data synchronization.
Push notifications let a messaging app alert you when a new text has arrived -- a key ability for Twitter's web app. File system access would let a photo or video editing web app use a photo stored on your machine for fast performance. Data synchronization means an app like Twitter can load online activity in the background so the app has fresh data as soon as you launch it.
Apple, though, is concerned about the downsides of such interfaces and risk they could undermine our trust in a web where it's mostly safe to click any link. Potential problems include security risks, like a hacked website getting access to files on your laptop, and annoyances like a barrage of website requests wanting us to grant them new powers.
Web apps start small
One of the cleverest features of a progressive web app is that it starts with a simple visit to a website, and that's a big reason Twitter likes the technology. There's no app store, just a gradual increase in the power of the web app as more aspects of it download -- for example, the settings page or direct message interface.
"It's small. When somebody sends you a link, you can quickly view it within seconds versus going through an app install process," said Patrick Traughber, a Twitter product manager. That's great for people using old Android phones, living in emerging markets or using a slower network.
With Google Chrome, Mozilla Firefox and Microsoft Edge -- except on Apple iPhones and iPads -- you'll sometimes see a prompt asking if you want to add the web app's icon to your home screen or desktop for later use.
That helps Twitter users who sampled the app dip back in later. And of course every developer wants people to use their app a lot.
What Twitter likes about web apps
Other things Twitter likes about its web app:
- It's smaller. The size isn't so important in wealthy countries, but it's a big deal in emerging markets.
- It's adaptable. Instead of plodding through app store approvals, Twitter updates its web app daily over the web, adding features and issuing fixes rapidly.
- With frequent updates, it's never out of date. That allows Twitter to experiment and quickly backtrack if something doesn't work.
- Developers can reach new operating systems like KaiOS quickly.
- It's easier to build. Twitter has one app that works on many devices, mostly adjusting automatically to things like different screen sizes.
"As a developer it's nice to be able to code once and have it work everywhere and for everyone," Croom said.
The Apple gap
But not everything is great in the world of web apps. On iPhones, there's no ability to send push notifications from websites, for example, and web apps can't prompt users to install them to their home screens. Background sync also is a no go.
The gap between the Twitter PWA and the Twitter native app is "more pronounced on iOS than on the Android side," Traughber said. Twitter would like Apple to lift its current restriction that third-party browsers must only use Apple's own browser engine, Croom added.
Twitter sees its mobile and web apps as complementary. But no matter how people use it, the web is core to Twitter. Each tweet is anchored to a single web address that, when shared, can open up a new world for people.
Web addresses -- URLs -- are a key part of the viral nature of the web. They can lead you to a company's website, an online word processing document or a videoconference with your coworkers. Web addresses even anchor us to experiences that take place off the web. Sharing a game on the Apple app store or a photo from the Instagram app? "Copy link" makes it happen.
And of course URLs can link to provocative tweets.
"The web is one of the most accessible and available platforms that exists for people to interact," Traughber said. "No matter where you are, when people receive a link, people can follow that link."